By ANNA JO BRATTONLINCOLN, Neb. (AP) - For two years, Bolivian scholar Waskar Ari has puzzled over why his request for a work visa to teach Latin American history in Nebraska wasn't approved.

After all, he had lived in the United States for a decade, receiving a doctorate from Georgetown University, teaching at Western Michigan University and working as a postdoctoral fellow at the University of Texas.

Then the U.S. Department of Homeland Security got involved.

Ari is one of a growing number of foreign scholars whose visas have been revoked, denied or delayed based on their ideology or political views, say civil rights groups and attorneys.

It's a frustrating process that discourages many talented scholars from coming to the United States, said Jameel Jaffer, director of the national security project for the American Civil Liberties Union.

Our concern is that the government is using immigration laws as a way of censoring the academic community, Jaffer said. Especially now, it's important that Americans not let the U.S. government act as a filter for ideas.

Ari's troubles began shortly after the University of Nebraska-Lincoln hired him in June 2005 to teach courses on Latin American history.

When he tried to re-enter the United States after a brief visit to Bolivia during summer 2005, he was told his visa petition had been delayed and that the U.S. Embassy in La Paz, Bolivia, had been told by the State Department to cancel all existing visas.

Ari said he was given no explanation and still doesn't know why the visas were canceled.

I came to Bolivia for a short family visit ... but since then the world has been upside down for me, Ari said by e-mail.

The university, which had petitioned the U.S. Citizenship and Immigration Services for Ari's visa and paid a $1,000 processing fee so he could enter the country in time to start teaching, decided to fight.

The university decided to make a stand on this, said Peter Levitov, the university's associate dean of international affairs. He's already considered part of the family in the history department.

UNL filed a lawsuit in U.S. District Court for the District of Columbia against the Department of Homeland Security, questioning whether the background checks the department is conducting on Ari are authorized by law and whether the department has the authority to withhold or delay action on the petition.

Even assuming the department has such authority, UNL maintains that 22 months is more than sufficient time to conclude background checks on a Bolivian academic who seeks merely to teach in the United States, according to a statement.

The department had a limited time to respond to the lawsuit, and on Thursday - near the deadline - approved Ari's petition for a work visa.

What we don't know is why they made that decision, said Michael Maggio, a Washington attorney representing the university. The department offered no explanation, and messages left for representatives at the department by The Associated Press weren't returned Friday. Department officials in the past have refused to comment on the case.

The change of heart could be because the department's legal counsel decided the authority couldn't be defended in court, Maggio said. Or the security checks may have been completed and Ari has been cleared of suspicion.

Ari is an expert in the history of indigenous peoples, especially in Bolivia, whose first indigenous president, Evo Morales, is an outspoken critic of the Bush administration's policies in the region and a supporter of Venezuelan President Hugo Chavez.

Ari said he met Morales once, at a large Indian youth meeting in Oruro sometime between 1979 and 1981. He forgot about the meeting until his visa troubles began and a friend reminded him.

Ari and Morales both are Aymara Indians - an indigenous people of Bolivia - but Ari said their political views differ.

While I am sure this is a terrible misunderstanding, I think it might be a wrong interpretation about my popular writing regarding indigenous rights in the Americas' history, Ari said.

Ari now must apply for a visa at the U.S. Consulate in La Paz. He hopes another round of security checks doesn't cause further delays.

I will only believe this nightmare has gone when I arrive to Lincoln, Ari said.

The ACLU says Ari's case is similar to that of Tariq Ramadan, a Swiss citizen and Muslim scholar who teaches at Oxford University. He was denied a temporary business and tourism visa in 2004 after the State Department said he provided material support to a terrorist organization.

The ACLU said the U.S. government told Ramadan he was being excluded because he donated $765 to French and Swiss organizations that provide humanitarian aid to Palestinians.

The ACLU is fighting Ramadan's exclusion in court and more broadly asking a federal judge to find it unconstitutional for government to exclude people on ideological grounds.

The history department at Nebraska is delighted with Homeland Security's decision to move along the process, said Ken Winkle, chairman of the department.

In the meantime, Ari is teaching at the Universidad Mayor de San Andres in Bolivia. Salaries are low, and Ari said he also does international consulting and gives talks throughout the country.

Ari wonders whether someone in Bolivia is trying to hurt him by saying wicked things about me to the U.S. security system, knowing that United States is sensitive to perceived connections with anti-American groups,

But Ari says he's looking forward to the day he can start teaching at Nebraska: I will wait whatever time is necessary. I know that this only a terrible misunderstanding and truth will come up at the end.